var mergeTwoList = function(l1,l2){
  let currency = new listNode()
  let dummy = currency
  if(l1 !== null && l2 != null){
    if( l1.val > l2.val){
      currency.next = l2;
      l2 = l2.next
    }else{
      currency.next = l1;
      l1 = l1.next
    }
    currency = currency.next
  }
  if(l1 != null){
    currency.next = l1
  }
  if(l2 != null){
    currency.next = l2
  }
  return dummy.next
}